In recent years, in an image forming apparatus such as a printer, a copying machine, or the like, of an electro photographic type, downsizing and improvement in operativity have been desired.
From the viewpoint of the improvement in operativity of the image forming apparatus, a process cartridge system in which a photosensitive member, a charging means, a developing means, a cleaning means, and the like are integrally assembled into a cartridge and the cartridge is detachably mountable to an image forming apparatus main assembly has been employed. By this cartridge system, the operativity was further improved, so that it became possible to easily perform maintenance of the above-described process means such as the developing means by a user himself (herself).
Similarly, an intermediary transfer member and the like of the image forming apparatus main assembly is also constituted as a unit and the unit is detachably mountable to the image forming apparatus main assembly to improve the operativity and a maintenance property.
Further, as the drive transmission device for stably transmitting a driving force to these units detachably mountable to the image forming apparatus main assembly with reliability, coupling performed by a combination of a projected portion XX and a corresponding recessed portion YY as shown in FIG. 26 has been used.
In Japanese Laid-Open Patent Application (Tokkai) 2005-157112, a constitution in which a coupling pair is interrelated with an openable cover or the like and by an opening operation of the cover, an apparatus main assembly-side coupling is retracted from a unit-side coupling to disengage the coupling pair thereby to permit mounting and demounting of the unit is disclosed.